Ultraviolet Radiation Induced DNA Damage in Bacterioplankton in the Southern Ocean

现在有强有力的证据表明，地球表面某些地区的紫外线辐射正在增加。主要关注的是南极洲和南大洋上空臭氧消耗的年度模式，与臭氧空洞事件发生前相比，臭氧水平下降了74%。研究表明，平流层臭氧浓度的降低会导致紫外线辐射水平的增加。臭氧耗竭引起的紫外线辐射增加对浮游植物和初级生产的影响已引起广泛的关注，而对细菌的影响却在很大程度上被忽视了。从先前在南大洋和其他地方的研究中可以明显看出，细菌在营养物质的矿化中起着至关重要的作用，并为高等生物提供了营养联系。本研究的目的是确定由紫外线辐射引起的浮游细菌的DNA损伤和臭氧消耗的函数，将DNA修复基因（recA）的诱导强度与损伤程度联系起来，并通过细菌组合估计应激对碳通量的影响。分子生物学在识别光产物和检查细胞DNA修复机制诱导方面的敏感新进展将与测量细菌生物量和产量的传统方法相结合。嘧啶-嘧啶酮（6-4）光产物和环丁烷二聚体是紫外线辐射产生的独特光产物。这些DNA损伤可以用放射免疫测定法来鉴别。recA基因在细菌中广泛分布且高度保守。由于该基因在修复受损DNA中的关键作用，其浓度和活性将被用作细菌对DNA损伤反应的直接测定。通过测量细菌生物量、生产和生长效率，将估计对细菌碳通量的微妙影响。该结果将为浮游生物种群中紫外线诱导的分子损伤数量和修复机制提供信息。紫外线a辐射和紫外线b辐射都会造成细胞损伤，而只有紫外线b辐射由于臭氧消耗而增强。通过同时分析DNA损伤和recA基因的诱导作为对损伤的一般反应，将紫外线b辐射的影响与其他DNA损伤机制进行对比。将提供关于对总产量的影响的更多资料，并进一步阐明南大洋细菌和浮游植物生产的相互作用。

9419037 Jeffrey There is now strong evidence that ultraviolet radiation is increasing over certain locations on the Earth's surface. Of primary concern has been the annual pattern of ozone depletion over Antarctica and the Southern Ocean where ozone levels have declined as much as 74% compared to pre-ozone hole events. Reduction of ozone concentration in the stratosphere has been shown to result in an increase levels of ultraviolet radiation. The impact of increased ultraviolet radiation due to ozone depletion upon phytoplankton and primary production has received extensive interest, while the effects on bacteria have been largely overlooked. It is apparent from previous studies in both the Southern Ocean and elsewhere that bacteria play a vital role in mineralization of nutrients and provide a trophic link to higher organisms. The objectives of this study are identify DNA damage in bacterioplankton resulting from ultraviolet radiation and as a function of ozone depletion, relate the intensity of the induction of DNA repair genes (recA) to the extent of damage, and estimate the effect of the stress on carbon fluxes through bacterial assemblages. Sensitive new advances in molecular biology to identify photoproducts and examine the induction of cellular DNA repair mechanisms will be coupled with traditional approaches for measuring bacterial biomass and production. Pyrimidine-pyrimidone (6-4) photoproducts and cyclobutane dimers are the unique photoproducts created by ultraviolet radiation. These DNA lesions may be identified using radioimmunoassays. The recA gene is wide spread and highly conserved among bacteria. Because of the pivotal role of this gene in repairing damaged DNA, its concentration and activity will be used as a direct assay of the bacterial response to DNA damage. With measurements of bacterial biomass, production and growth efficiency, subtle effects on bacterial carbon fluxes will be estimated. The results will provide information on the amount of UV induced molecular damage and repair mechanisms in planktonic populations. Both ultraviolet-A radiation and ultraviolet-B radiation create cellular damage, while only ultraviolet-B radiation is enhanced as a result of ozone depletion. Through simultaneous analysis of DNA damage and the induction of the recA gene as a general response to damage, the effect of ultraviolet-B radiation will be contrasted with other mechanisms of DNA damage. Additional information will be provided on the effects on total production and further elucidate the interactions of bacteria and phytoplankton production in the Southern Ocean.